You can't say that. WWI began because of the assassination of Archduke Franz Ferdinand of Austria. There still would have been a war. It remains to be seen if Germany would have won WWI if no other country entered that war against Germany. It was the Treaty of Versailles that was used as the catalyst by Hitler to wage war once again. He hated the French the most because of that Treaty, and he blamed the Jews for the loss and the state of Germany's economy in the aftermath of that war. If Britain hadn't fought in WWI, it's still possible that Germany wouldn't have been victorious during that war, so there would still have been a Treaty for Hitler to use as an excuse to use force on the rest of the world.
WWI began because of the assassination of Archduke Franz Ferdinand of Austria. There still would have been a war.
Not if the Brits told the French and Belgians to ‘flip off’.
Screw the French, would things have been any worse if the Germans defeated the French in 1914? Heck, we might never have had to deal with Vietnam.